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boost::iostreams 3

Enic — Sun, 28 Jul 2013 15:02:00 GMT

boost的iostreams�l��g基本上诠释了stream的概念，但是考虑东西��g��太多了，不管怎么样都得好好学学他的思想。此番重新学习一下�?/p>

模板的世界比较篏�Q�先从OOP的视角看看：

咋看一下似乎也没多��东西，是库的作者拿了一堆基��概念在那玩文字游戏好像�?/p>

抽象��h��应该是这样几个东东：IIOStream IIStream IOStream IInSeek IOutSeek IIOSeek IStreamInFilter IStreamOutFilter IStreamIOFilter

看�v来确实有�Ҏ��心，理论和现实是有差距的�Q�，�Q�唉�Q�，�Q?/p>

接下来让他更恶心一点，应�ؓ�q�缺��一个Filterable的概�?/p>

很快出来一张蜘蛛网�Q�，�Q�这也不能说�q�度设计吧，也许有些�pȝ��需要这么细化呢�Q?/p>

不过看到�q�张蜘蛛�|�之后果断决定我后面�l�手�l�对不要�q�么负责�Q�可以考虑v��的做法�Q�接口都是全的，但是功能不一定，使用的不支持的接口就弄个提示啥的。。�?/p>

�q�样看上��L��那么回事了，�Q�，seek被提炼到stream里边�Q�filter��d��sink的概念，或者直接用delegate更合适？

Enic 2013-07-28 23:02 发表评论

Enic — Mon, 19 Nov 2012 08:17:00 GMT

原因�Q?/p>

1.文档不够完善

2.熟悉�E�度不够�Q�学习曲�U�比较陡峭，直接用有可能失控

3.实现太过复杂�Q�还需要mpl库的支持

4.如果使用�Q�iostreams��成为底层，整个��目都会对其依赖�Q�有风险

5.说白了，�q�是能力不够�Q�不�q�了解了一些iostreams归纳出来的concepts也是非常有收货�?/p>

6.�|�上的一句归�U�I��

在真正掌握模版之前尽量少�?/span>

//////////////////////////////////////////////

Device Concepts

The most important Device concepts are these:

Device: Base for all Device concepts, provides associated character type and category.
Source: Provides read-only access to a sequence of characters.
Sink: Provides write-only access to a sequence of characters.
BidirectionalDevice: Provides access to two separate sequences of characters, one for reading and the other for writing.
SeekableDevice: Provides read-write access to a single sequence of characters, with a single repositionable read/write head.

Filter Concepts

The most important Filter concepts are these:

Filter: Base for all Filter concepts, provides associated character type and category.
InputFilter: Filters characters read from a Source.
OutputFilter: Filters characters written to a Sink
BidirectionalFilter: Filters two separate character sequences, one read from a Sink and the other written to a Sink.
SeekableFilter: Filters a single characters sequence, controlled by a SeekableDevice, providing filtered input, output and random access with a single repositionable read/write head

Optional Behavior

Boost.Iostreams prvides several concepts corresponding to optional behavior that a Filter or Device might implement:

Blocking: A Device which blocks when it receives a read or write request until all requested characters are available, or until the end of a stream is reached.
Direct: A Device which provides access to its controlled sequences as regions of memory rather than via a socket-like interface.
Closable: A Filter or Device which receives notifications immediately before a stream is closed.
Flushable A Filter or Device which receives notifications when a stream is flushed.
Localizable: A Filter or Device which receives notifications when the locale of a stream or stream buffer is set using basic_ios::imbue or basic_streambuf::pubimbue.
Multi-Character: A Filter which provides access to its controlled sequences several characters at a time, via a socket-like interface.
OptimallyBuffered A Filter or Device which will be fitted with a buffer of custom size if no buffer size is explicitly requested by the user.
Peekable: A source which allows characters to be put back to the input sequence.
Pipable: A Filter which can appear in pipelines.

Enic 2012-11-19 16:17 发表评论

1.modes

Enic — Mon, 19 Nov 2012 03:49:00 GMT

mode�Q�模式？�Q�：
    input: 使用一个character队列�Q�用来输�?br>    output: 使用一个character队列�Q�用来输�?br>    bidirectional: 使用两个character队列�Q�分别用来输入、输�?br>    input-seekable: 使用一个character队列用来输入�Q�包含一个读索引游标
    output-seekable: 使用一个character队列用来输出�Q�包含一个写索引游标
    seekable: 使用一个character队列用来输入输出�Q�包含一个读/写复用的索引游标
    dual-seekable: 使用一个character队列来输入输出，包含两个索引游标分别用来标识��d��
    bidirectional-seekable: 使用两个character队列分别用来输入输出�Q�同时每个队列包含一个各自的索引游标
    *blocking: 如果读请求永�q�比剩下的character��除了end情况�Q�而且写请求需要的永远比现有的��。那��是一个blocking�?br>The Blocking concept does not apply to filters. Instead, filters are required to be blocking-preserving, which means that

a read request never produces fewer characters than requested unless end-of-stream has been reached or unless a read request to a downsteam Source produces fewer characters than requested, and
a write request never consumes fewer characters than requested unless a write request to a downsteam Sink consumes fewer characters than requested.

*如果熟悉stl应该��׃��解traits技术（应该是技巧）

�q�里是boost::iostream库的traits

�q�有个模版元函数mod_of

Enic 2012-11-19 11:49 发表评论